Many devices such as computers and televisions require the use of a display. Typically, the cathode ray tube (CRT) has been used to perform this function. The CRT consists of a scanning electron gun directed toward a phosphor-coated screen. The electron gun emits a stream of electrons that impinge upon individual phosphor picture elements or pixels on the screen. When the electrons strike the pixels, they cause the energy level of the phosphor to increase. As the energy level declines from this excited state, the pixels emit photons. These photons pass through the screen to be seen by a viewer as a point of light. The CRT, however, has a number of disadvantages. In order to scan the entire width of the screen, the CRT screen must be relatively distant from the electron gun. This makes the entire unit large and bulky. The CRT also requires a significant amount of power to operate.
More modem devices such as laptop computers require a light weight, portable screen. Currently, such screens use electroluminescent or liquid crystal display technology. A promising technology to replace these screens is the field emission display. The field emission display (FED) utilizes a baseplate of cold cathode emitter tips as a source of electrons in place of the scanning electron gun used in the CRT. When placed in an electric field, these emitter tips emit a stream of electrons in the direction of a faceplate to which phosphor pixels are adhered. Instead of a single gun firing electrons at the pixels, the FED has an array of emitter tips. Each of the emitter tips are individually addressable, and one or more of the emitter tips correspond to a single phosphor pixel on the faceplate.
One of the problems associated with an FED is that not all of the photons that are released from the pixels pass through the faceplate to be seen by the viewer as points of light. Rather, nearly half of the photons will proceed in the general direction of the baseplate, and may impinge upon the emitter tips and/or circuitry within the FED. This may cause an undesirable photoelectric effect, and any reflected light from the baseplate reduces the contrast of the FED. A further problem is that not all of the electrons released by the emitter tips actually excite their targeted pixel. Instead, some of these electrons are reflected internally, and may excite a non-targeted pixel.
Accordingly, there is a need in the art for a field emission display which minimizes the photoelectric effect, and the problems associated with internally-reflected electrons. The present invention fulfills these needs, and provides other related advantages.